The present invention relates to color image sensor devices such as image scanners, facsimile machines and copy machines, and in particular relates to compression techniques in conjunction with such image acquisition devices.
Many different types of devices exist for sensing color images. These can be desktop or hand held scanners, copy machines, facsimile machines, or other devices. A number of different methods are used. In one, a fluorescent lamp is used to illuminate the image, with different color filters being positioned to intercept either the transmitted or reflected light before it is sensed. Alternately, multiple fluorescent lamps with their own dedicated filters used for emitting different colors of light could be used. In yet other devices, instead of fluorescent lamps, light-emitting diodes (LEDs) are used, with different LEDs having different color emissions. For example, a typical configuration might have three types of LEDs, one in the blue range of wavelengths, another in the green range of wavelengths, and another in the red range of wavelengths.
One problem with existing scanning techniques is the large amount of data that needs to be acquired and stored or transmitted to a computer. Typically, each pixel in the image must be digitized three (or more) times, for each of the desired color components (RGB). This consumes a significant amount of time for scanning the image, and also requires a large amount of data be stored or transmitted. In a typical embodiment, each line of the image is read first with red light, then with green, then with blue, and then the scanner moves on to the next line. Existing compression methods require additional time to reduce the amount of data actually stored or transmitted.